module Sass::Script::Functions

def abs(value)
  numeric_transformation(value) {|n| n.abs}
end

def ceil(value)
  numeric_transformation(value) {|n| n.ceil}
end

def floor(value)
  numeric_transformation(value) {|n| n.floor}
end

def hsl(hue, saturation, lightness)
  original_s = saturation
  original_l = lightness
  # This algorithm is from http://www.w3.org/TR/css3-color#hsl-color
  h, s, l = [hue, saturation, lightness].map { |a| a.value }
  raise ArgumentError.new("Saturation #{s} must be between 0% and 100%") if s < 0 || s > 100
  raise ArgumentError.new("Lightness #{l} must be between 0% and 100%") if l < 0 || l > 100
  h = (h % 360) / 360.0
  s /= 100.0
  l /= 100.0
  m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s
  m1 = l * 2 - m2
  Color.new([hue_to_rgb(m1, m2, h + 1.0/3),
             hue_to_rgb(m1, m2, h),
             hue_to_rgb(m1, m2, h - 1.0/3)].map { |c| (c * 0xff).round })
end

def hue_to_rgb(m1, m2, h)
  h += 1 if h < 0
  h -= 1 if h > 1
  return m1 + (m2 - m1) * h * 6 if h * 6 < 1
  return m2 if h * 2 < 1
  return m1 + (m2 - m1) * (2.0/3 - h) * 6 if h * 3 < 2
  return m1
end

def numeric_transformation(value)
  unless value.is_a?(Sass::Script::Number)
    calling_function = caller.first.scan(/`([^']+)'/).first.first
    raise Sass::SyntaxError.new("#{value} is not a number for `#{calling_function}'")
  end
  Sass::Script::Number.new(yield(value.value), value.numerator_units, value.denominator_units)
end

def percentage(value)
  unless value.is_a?(Sass::Script::Number) && value.unitless?
    raise ArgumentError.new("#{value} is not a unitless number")
  end
  Sass::Script::Number.new(value.value * 100, ['%'])
end

def rgb(red, green, blue)
  [red.value, green.value, blue.value].each do |v|
    next unless v < 0 || v > 255
    raise ArgumentError.new("Color value #{v} must be between 0 and 255 inclusive")
  end
  Color.new([red.value, green.value, blue.value])
end

def round(value)
  numeric_transformation(value) {|n| n.round}
end